Protective film for minimization of shield and pole tip recession in thin film shielded read heads and write heads

ABSTRACT

A magnetic head having an enhanced recession resistance characteristic, and a method of fabricating the magnetic head having the enhanced recession resistance characteristic is disclosed. The improvement is the addition of one or more hard protective layers exposed edgewise at the media-head interface. Each protective layer is formed between the substrate and the top closure of the magnetic head to a thickness of greater than approximately 0.2 micrometers and a hardness of greater than approximately 850 Knoop. The protective layers are formed by depositing a hard metal film above, below or within the read and write transducers inside the magnetic head. The hard metal film is selected for its hardness, ease of use during the fabrication process, and compatibility with adjoining materials. The hard metals include, but are not limited to, chromium, iridium, rhodium, tantalum, titanium and tungsten.

TECHNICAL FIELD

The present invention relates to the field of magnetic read and writeheads used for tape and disk applications.

BACKGROUND ART

Magnetic heads used in magnetic tape applications generally consist ofone or more thin film magnetic transducers fabricated on a substrate andmounted with a closure. In the transducer fabrication process, a thickovercoat layer of alumina is deposited between the magnetic transducersand the top closure. The thin film magnetic transducers include readtransducers and write transducers. Read transducers typically have amagnetoresistive film, giant magnetoresistive film, or an inductiveelement for sensing data written in magnetic media. Write transducersare always inductive in nature for writing on the magnetic media.Multiple magnetic heads are often bound together to provide simultaneousread and write capabilities in tape drive applications.

The magnetic tape media is biased against the face of the magnetic heador heads as the media is moved longitudinally relative to the magneticheads. Rubbing between the tape media and the magnetic heads causes bothitems to wear. The substrates and closures of the magnetic heads arefabricated from hard materials to help minimize their wear. The magnetictransducers and overcoat layers, on the other hand, are fabricated frommaterials selected primarily for their magnetic and electricalproperties. (Magnetic transducer wear is not a major problem in harddisk applications because the magnetic transducers fly above the harddisk surface on a very thin layer of air.)

The difference in hardness between the substrate and closure, on the onehand, and the magnetic transducer materials and overcoat layermaterials, on the other hand, results in uneven wear at the face of themagnetic head due to contact with the magnetic tape media. Since themagnetic transducer materials and overcoat layer materials are softerthan the substrate and closure materials, the magnetic transducers andovercoat layers recess quicker from the media-head interface than do thesubstrate and closure. As a result, a concave shaped gap develops overtime between the magnetic transducer and the magnetic tape media. Thisgap causes poor read and write performance, and even total failure ofthe magnetic heads in severe recession cases.

Historical attempts to minimize wear of the magnetic transducermaterials have involved the utilization of harder materials in thevarious layers that make up the magnetic transducer. For example,cobalt-zirconium-tantalum alloys and iron-aluminum-nitrogen alloys havebeen used in place of the softer nickle iron alloys as the magneticshields and poles in magnetic read transducers and magnetic writetransducers respectively. In another example, alumina has been used inplace of the softer silicon dioxide as a nonmagnetic bulk insulatingmaterial and write gap layer material. However, the selection of hardermaterials for wear resistance usually remains a secondary considerationbehind the magnetic and electrical properties that determine the datarecording density. What is desired is a new approach that improves theerosion characteristics of the magnetic heads without addingconsiderable complexity to the magnetic head fabrication process orrequiring a tradeoff of the magnetic read and write performances.

DISCLOSURE OF INVENTION

The present invention is an improved method of fabricating magneticheads and the resulting magnetic head structures. The improvement is theaddition of one or more protective layers exposed edgewise at themedia-head interface. Each protective layer is situated inside,adjoining or adjacent the magnetic transducers disposed within amagnetic head. Each protective layer is formed from a metal that isharder than the neighboring magnetic layers and insulating layers. Thehard protective layer slows the rate at which the magnetic transducerserode and thus prolongs the life of the magnetic head.

Each protective layer added to the magnetic heads adds one extradeposition step to the fabrication process. The protective layers aredeposited to a thickness ranging from greater than 0.2 micrometers toapproximately 0.5 micrometers each. Thinner protective layers tend tooffer insufficient resistance to erosion. Thicker protective layersprovide only marginally better performance. Protective layer metals areselected based upon their hardness, ease of use during fabrication, andcompatibility with adjoining materials. The protective layers require ahardness of greater than 850 Knoop to be harder than sputtered alumina,the current industrial standard. The metals include, but are not limitedto, chromium, iridium, rhodium, tantalum, titanium and tungsten. Eachprotective layer may be patterned after deposition, as necessary, toopen vias and to provide electrical isolation from other conductivelayers.

Accordingly, it is an object of the present invention to provide animproved magnetic head having enhanced recession resistancecharacteristic. The improved may be applied to read-only, write-only,and combination read-write magnetic head configurations.

Another object of the present invention is to provide an improved methodfor fabricating the magnetic heads to provide the enhanced recessionresistance characteristic.

These and other objects, features and advantages will be readilyapparent upon consideration of the following detailed description inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a profile of a first embodiment of a magnetic read headfabricated according to the present invention;

FIG. 2 is a profile of the first embodiment of the magnetic read headshowing recession;

FIG. 3 is a profile of a second embodiment of the magnetic read head;

FIG. 4 is a profile of a third embodiment of the magnetic read head;

FIG. 5 is a profile of a first embodiment of a magnetic write headfabricated according to the present invention;

FIG. 6 is a profile of a second embodiment of the magnetic write head;

FIG. 7 is a profile of a third embodiment of the magnetic write head;

FIG. 8 is a profile of a fourth embodiment of the magnetic write head;and

FIG. 9 is a profile of a combination magnetic read and write headfabricated according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Several terms are used in this document in a generic sense. The term“forming” is meant to include any combination of fabrication steps thatresult in the deposition and patterning of a layer. This includesdepositing a layer followed by a subsequent patterning using a maskinglayer to control the removal of unwanted material. It also includes thedeposition of a patterning mask layer used to control a subsequentdeposition. The term “deposition” is any method of creating a layer ofmaterial on the existing surface. Deposition includes sputtering,evaporation, chemical vapor deposition, plating and other like methodsknown in the art. The term “patterning” is any method of defining ageometric area or areas where a layer will and will not exist.Patterning includes wet chemical etching, electrochemical machining,lift off techniques, ion milling, focused ion beams and other likemethods used in the art. The figures used in the discussion of theinvention are enlarged for illustrative purposes and are not drawn toscale.

A profile of a magnetic read head 100 fabricated according to thepresent invention is shown in FIG. 1. The magnetic read head 100 has amagnetic read transducer 102 situated between a top closure 104 and asubstrate 116 The read transducer 102 includes a sensor element 108 thatmay be a magnetoresistive film, a giant magnetoresistive film, or othermagnetically sensitive device known in the art. A top shield 110 and abottom shield 112 are provided above and below the sensor element 108respectively to improve the spatial resolution of the sensor element108. Insulator 114 separates the sensor element 108 from the top shield110 and the bottom shield 112. Substrate 116 provides a base upon whichthe transducer 102 is fabricated. An undercoat 118 is generally,although not necessarily, provided between the substrate 116 and thebottom shield 112. An overcoat 120 is formed on the top shield 110 andthen lapped flat to provide a planar surface to bond to the top closure104. One edge of the top closure 104, overcoat 120, read transducer 102,undercoat 118, and substrate 116 collectively form a media bearingsurface 122 for the magnetic read head 100.

The present invention is the addition of one or more protective layerssituated between the substrate 116 and the top closure 104 andinterfacing with the media bearing surface 122. FIG. 1 shows the firstand preferred embodiment of the magnetic read head 100 where a singleprotective layer 90 is provided between the top shield 110 and theovercoat 120. In alternative embodiments, the number and positions ofthe protective layers may be varied to provide the desired recessionresistance characteristics for the magnetic read head 100. Severalalternative embodiments will be described later. The presence or absenceof the closure 104 is independent of the present invention and areincluded for illustrative purposes only.

The protective layer 90 is formed by depositing and patterning, ifnecessary, a hard metal film. Patterning may be required to open vias(not shown) in the protective layer 90 and to provide electricalisolation from other conductors (not shown) running vertically withinthe magnetic read head 100. Deposition of the protective layer 90 may beaccomplished by any means known in the art such as sputtering,evaporation, chemical vapor deposition, plating and the like. Likewise,patterning of the protective layer 90 may be accomplished by any meansknown in the art such as wet and dry chemical etching, lift off, ionmilling, reactive ion etching, plating masks and the like. The onlylimitation on the deposition and patterning processes is compatibilitywith the layers on which the protective layer 90 is formed.

Thickness of the protective layer 90 is typically 0.5 micrometers. Thethickness may be increased or decreased depending upon the desiredrecession resistance characteristics, the number of other protectivelayers provided, the type of metals being employed, positioning of theprotective layer 90 with respect to the other layers, and cost. Apractical minimum thickness for the protective layer 90 is approximately0.2 micrometers. Improvements in the recession resistancecharacteristics provided by a thinner protective layer usually do notjustify the added expense of forming that protective layer.

Protective layer 90 may be formed from a single metal or a metal alloy.The metals are chosen for their hardness, ease of deposition, easy ofpatterning, compatibility with other materials they contact, and theirability to adhere with neighboring layers. The hardness of theprotective layer 90 is selected to be greater than that of the readtransducer 102 and overcoat 120. Compatibility with other materialsincludes diffusion of the protective layer 90 into the neighboringmaterials, or vice versa, that may change the properties of therespective layers. Compatibility may also include galvanometricdifferences between the protective layer 90 and the adjoining materialsthat can result in corrosion.

Near the end of the magnetic read head's 100 fabrication process, theside of the head that is to face the magnetic media (not shown) islapped to create a smooth surface. This smooth surface is referred to asan air bearing surface in disk drive heads, and a tape bearing surfacein a tape drive head. This document refers to the lapped surface as themedia bearing surface 122 in a generic sense. Lapping of the mediabearing surface 122 results in recession of the read transducer 102 andthe overcoat layer 120, as shown in FIG. 2. Recession is caused by theread transducer 102 and the overcoat layer 120 eroding at a faster ratethan the relatively harder substrate 116 and top closure 104.

Common magnetic materials used in the fabrication of the read transducer102 include Permalloy (80:20 NiFe) and Cobalt Zirconium Tantalum (CZT).Alumina is the industrial standard nonmagnetic material for theinsulating layer 114 and overcoat layer 120. Plated Permalloy is thesoftest of these three materials with a hardness of approximately 660Knoop. Vacuum deposited CZT has a hardness of approximately 740 Knoop.Sputtered alumina is harder at approximately 850 Knoop. For comparison,the substrate 116 and top closure 104 are often, although notnecessarily, made of AlTiC that has a hardness of approximately 2480Knoop.

Table I shows the initial shield recession, indicated by dimension 124,of four sample magnetic read heads 100 caused by lapping the mediabearing surface 112. All four samples were fabricated for use withmagnetic tapes (not shown). Sample 1 and sample 2 were fabricatedwithout the protective layer 90. Sample 3 and sample 4 include a 0.5micrometer tantalum protective layer 90 vacuum deposited on the topshield 110. After lapping, the measured shield recession 124 of the foursamples ranged from 8 to 10.6 nanometers in depth. Sample 1 and sample 2were then mounted flanking a magnetic write head in a firstread-write-read group. Likewise, sample 3 and sample 4 where mounted ina second read-write-read group.

Five million feet of magnetic tape were then moved across each of thetwo combined heads to simulate normal operation. The final shieldrecessions 124, ranged from 10.2 to 21 nanometers, as shown in Table I.Recession increase was calculated by the formula 100×(finalrecession−initial recession)/initial recession. Note that the presenceof the protective layer 90 in sample 3 and sample 4 resulted insignificantly lower shield recession increases.

TABLE 1 Shield Recession Test Results CZT shield without a CZT shieldwith Protective Layer Ta Protective Layer Sample 1 Sample 2 Sample 3Sample 4 Initial recession (nm) 8 9.6 10.6 10.2 Final recession (nm) 2114.8 11.5 10.2 Recession increase (%) 162 54 8.5 0.0

The improved recession resistance characteristics of sample 1 and sample2 are attributable to the approximate 930 Knoop hardness of the titaniumprotective layer 90 as compared with the approximately 740 Knoophardness of the top shield 110 and the approximately 850 Knoop (820 on aVickers scale) hardness of the overcoat layer 120. Other metals that arereadily available and well suited to thin film fabrication include, butare not limited to chromium (935 Knoop), iridium(1760 Vickers), rhodium(1246 Vickers), tantalum (875 Knoop), and tungsten (1400 Knoop).

The protective layer 90 may be located anywhere in proximity to the readtransducer 102. Here, proximity means anywhere between the substrate 116and the top closure 104, if present. When the magnetic read head 100does not include a top closure 104, then the protective layer 90 may beanywhere from next to the substrate 116 to being the top layer. FIG. 3and FIG. 4 show two alternative embodiments where the protective layer90 is situated at other locations between the substrate 116 and the topclosure 104.

FIG. 3 is a profile of a second embodiment of a magnetic read headfabricated in accordance with the present invention. Here the protectivelayer 90 exists between the bottom shield 112 and the substrate 116.This placement of the protective layer 90 improves the shield recessionresistance characteristics of the bottom shield 112. The resultingimprovement, though, is often limited due to the closeness of the hardsubstrate 116 that also operates to help reduce the recession of thebottom shield 112 in conventional configurations. To improve therecession resistance characteristics of both shields 110 and 112, twoprotective layers 90 could be formed, one below the bottom shield 112,as shown in FIG. 3, and a second formed above the top shield 110, asshown in FIG. 1.

FIG. 4 is a profile of a third embodiment of the magnetic read headfabricated in accordance with the present invention. Here the protectivelayer 90 is embedded within the read transducer 102 between the sensorelement 108 and the top shield 110. Insulating layer 114 extends betweenthe sensor element 108 and the protective layer 90 to prevent anelectrical short circuit of the sensor element 108 by the protectivelayer 90. This third embodiment offers better recession protection forthe sensor element 108 than the first and second embodiments shown inFIG. 1 and FIG. 3 respectively when the same thickness protective layer90 is used. The better recession protection is due to the closerpositioning of the protective layer 90 to the sensor element 108. Onedisadvantage of the third embodiment is that the spacing between thesensor element 108 and the shields 110 and 112 are becoming smaller witheach new generation of read transducer 102. Consequently, the protectivelayer 90 must be made thinner thus diminishing its ability to slowerosion and recession.

The present invention may also be applied to a magnetic write head 200,as shown in part in FIG. 5. Similar to the magnetic read head 100, themagnetic write head 200 consists of a write transducer 202 fabricated onthe substrate 116 or undercoat layer 118, topped by the overcoat layer120, and mounted with the top closure 104. The write transducer 202usually, although not necessarily, consists of a bottom pole 226 and atop pole 228 separated from each other at the media bearing surface 122by a nonmagnetic write gap layer 230. A coil 232 disposed between thetop pole 228 and bottom pole 226 induces a magnetic flux in the poles228 and 226 that fringe around the write gap layer 230 at the mediabearing surface 122 to write in the magnetic media (not shown).

The present invention is the addition of one or more protective layers92 proximate the write transducer 202, anywhere between the substrate116 and top closure 104 and exposed at the media bearing surface 112.FIG. 5 shows the first and preferred embodiment where the protectivelayer 92 is situated overlaying the top pole 228. Protective layer 92 isformed by depositing a metal or metal alloy overlaying the top pole 228.The protective layer 92 is then patterned to avoid electrical andmechanical interference with electrical leads (not shown) that connectto the coil 232 and possibly other layers not shown. Protective layer 92in the magnetic write head 200 provides the same erosion protection tothe top pole 228 that the protective layer 90 in the magnetic read head100 provides to the top shield 110. By forming the protective layer 92of a harder material than the top pole 228 and overcoat layer 120, therecession rate of the top pole 228 is reduced. Since typical magneticmaterials for the write transducer's poles 226 and 228 are Permalloy andCZT, the same metals used for the protective layer 90 or layers in themagnetic read head 100 can be used for the protective layer 92 or layersin the magnetic write head 200.

FIG. 6 and FIG. 7 are profiles of a second and third embodiment of themagnetic write head respectively fabricated in accordance with thepresent invention. In the second embodiment shown in FIG. 6, theprotective layer 92 is located between the substrate 116 and the bottompole 226. This configuration provides better recession resistancecharacteristics for the bottom pole 226, but again the full effect tothe protective layer 92 in this position is overshadowed by the nearbyhard substrate 116. In the third embodiment shown in FIG. 7, theprotective layer 92 is located between the top pole 228 and the writegap layer 230. In this case, if the protective layer 92 is nonmagneticthen it operates as part of the write gap distance, distance 233,between the pole tips of the top pole 228 and bottom pole 226 at themedia bearing surface 122.

FIG. 8 is a profile of a third embodiment of the magnetic write headfabricated in accordance with the present invention. In this embodiment,the protective layer 92 and the write gap layer 230 are one in the same.This configuration potentially simplifies the fabrication process sincethe inclusion of the protective layer 92 may add no additional steps.The protective layer 92 material is deposited and patterned in place ofthe industrial standard alumina. Because of its operation as the writegap, the protective layer 92 in this third embodiment must be formedfrom a nonmagnetic material, such as the metals listed earlier. Since ametal write gap layer 230/protective layer 92 is electricallyconductive, an electrical insulator must be provided between this layerand the coils 232 to prevent electrical short circuiting of the coils232. This is accomplished by a planarization layer 234 that is normallyformed overlaying the write gap layer 230 anyway to provide a planarsurface on which the coils 232 are fabricated. Alternatively, the writegap layer 230/protective layer 92 may be patterned to reside in the zerothroat area, shown as area 236, only. This design still requires thatthe planarization layer 234 or other insulating layer be formed over thebottom pole 226 to isolate the coils 232 from the bottom pole 226electrically.

The present invention may be applied to magnetic heads having multipletransducers disposed between the substrate 116 and the overcoat 120.FIG. 9 shows a common multiple transducer configuration where a writetransducer 202 is fabricated on top of a read transducer 102 to form acombined magnetic head 300. FIG. 9 also shows an example of a magnetichead having multiple protective layers, in particular, a firstprotective layer 94 and a second protective layer 96.

Within the combination magnetic head 300, the read transducer 102 and awrite transducer 202 normally share a common magnetic layer (not shown).This common magnetic layer acts as both the top shield 110 of the readtransducer 102, and as the bottom pole 226 of the write transducer 202.While this approach saves on fabrication complexity by forming only onelayer for both transducers, there is a tradeoff in transducerperformance. From the write transducer's 202 perspective, the commonmagnetic layer should have a high saturation magnetizationcharacteristic for compatibility with high coercivity magnetic media.From the read transducer's 102 perspective, the common magnetic layershould have a high permeability for shielding the sensor element 108from stray magnetic fields and a stable magnetic domain configuration.Existing magnetic materials used in thin film transducer fabricationtend to have excellent characteristics for one of these applications,but not both simultaneously.

Adding the first protective layer 94 to the combined magnetic head 300provides a mechanism that allows the top shield 110 and the bottom pole226 to be fabricated from different magnetic materials. The top shield110 may be formed from a high permeability material and the bottom pole226 from a high magnetization saturation material with a stable magneticdomain configuration. First protective layer 94 acts as barrier thatprevents the two different magnetic materials from inter-diffusingduring fabrication and life span of the combined magnetic head 300.First protective layer 94 also provides recession protection for boththe write transducer 202 and the read transducer 102. The secondprotective layer 96 is formed above the top pole 228. In this example,an extra insulating layer 238 of alumina is deposited and patternedbetween the top pole 226 and the second protective layer 96. This allowsthe second protective layer 96 to be electrically isolated from the toppole 228 if required.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

What is claimed is:
 1. A magnetic head having a media bearing surface,the magnetic head comprising: a substrate, at least one edge of thesubstrate defining the media bearing surface; an overcoat overlaying thesubstrate; a magnetic read transducer disposed between the substrate andthe overcoat and interfacing edgewise with the media bearing surface,the magnetic read transducer including a shield made of a first magneticmaterial; a magnetic write transducer disposed between the substrate andthe overcoat, the magnetic write transducer including a pole made of asecond magnetic material different than the first magnetic material; anda protective layer of metal having a thickness greater thanapproximately 0.2 micrometers and a hardness greater than approximately850 Knoop, the protective layer being sandwiched between the shield andthe pole and interfacing edgewise with the media bearing surface, theprotective layer further acting as a barrier that prevents the first andsecond magnetic materials from inter-diffusing during fabrication of themagnetic head, wherein the protective layer is not a write gap layer. 2.The magnetic head of claim 1 wherein the protective layer is disposedbetween the substrate and the magnetic write transducer.
 3. The magnetichead of claim 1 wherein the protective layer includes metal selectedfrom a group of metals consisting of chromium, iridium, rhodium,tantalum, titanium and tungsten.
 4. A magnetic head having a mediabearing surface, the magnetic head comprising: a substrate, at least oneedge of the substrate defining the media bearing surface; an overcoatoverlaying the substrate; a magnetic read transducer disposed betweenthe substrate and the overcoat, the read transducer including a shieldmade of a first magnetic material; a magnetic write transducer disposedbetween the substrate and the overcoat and interfacing edgewise with themedia bearing surface, the write transducer having a write gap layer anda pole made of a second magnetic material different than the firstmagnetic material; and a protective layer for improving recessionresistance characteristics of the magnetic head, the protective layerhaving a thickness greater than approximately 0.2 micrometers and ahardness greater than approximately 850 Knoop, the protective layercomprising metal and being sandwiched between the shield and the polesuch that the protective layer acts as a barrier that prevents the firstand second magnetic materials from inter-diffusing during fabrication ofthe magnetic head, the protective layer further interfacing edgewisewith the media bearing surface, wherein the protective layer is separatefrom the write gap layer.
 5. The magnetic head of claim 4 wherein theprotective layer includes metal selected from a group of metalsconsisting of chromium, iridium, rhodium, tantalum, titanium andtungsten.